The characteristics of bismuth-niobium-oxide (BNO) films prepared using a solution process were investigated. The BNO film annealed at 550 °C involving three phases: an amorphous phase, Bi_3NbO_7 fluorite microcrystals, and Nb-rich cubic pyrochlore microcrystals. The cubic pyrochlore structure, which was the main phase in this film, has not previously been reported in BNO films. The relative dielectric constant of the BNO film was approximately 140, which is much higher than that of a corresponding film prepared using a conventional vacuum sputtering process. Notably, the cubic pyrochlore microcrystals disappeared with increasing annealing temperature and were replaced with triclinic β-BiNbO_4 crystals at 590 °C. The relative dielectric constant also decreased with increasing annealing temperature. Therefore, the high relative dielectric constant of the BNO film annealed at 550 °C is thought to result from the BNO cubic pyrochlore structure. In addition, the BNO films annealed at 500 °C contained approximately 6.5 atm. % carbon, which was lost at approximately 550 °C. This result suggests that the carbon in the BNO film played an important role in the formation of the cubic pyrochlore structure.

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Copyright 2014 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Satoshi Inoue,Tomoki Ariga, Shin Matsumoto, Masatoshi Onoue, Takaaki Miyasako, Eisuke Tokumitsu, Norimichi Chinone, Yasuo Cho, and Tatsuya Shimoda, Journal of Applied Physics, 116(15), 154103 (2014) and may be found at http://dx.doi.org/10.1063/1.4898323